Solution-processed ZnO thin film with high-density quantum dots via particle size control strategy

Abstract

Solution-derived ZnO quantum dot is one of the most widely used electron-transport layers in optoelectronic devices. To achieve high-efficiency in optoelectronic devices it is required that a thin film of ZnO quantum dot with low surface roughness and low defect intensity is developed. Herein, alcoholic solvents with different alkyl lengths were utilized to dissolve tetramethylammonium hydroxide to fine-tune the polarity of the solution, to achieve ZnO quantum dots with controllable particle size and monodisperse in alcohol solvents. Two kinds of ZnO quantum dots with particle sizes of 6 and 12 nm detected by dynamic light scattering were successfully prepared by this method. Furthermore, by mixing these two types of quantum dots, ZnO films with a different packing mode were fabricated, which exhibited lower surface defect density and surface roughness. This approach offers a novel pathway to reduce issues such as current leakage associated with ZnO as an electron-transport layer. What's more, the small particle size ZnO quantum dots effectively fill the gaps between the large particle size quantum dots, resulting in a film with a higher density of quantum dots. This increased density contributes to the higher electrical conductivity of the ZnO film.